Counter flow cooling drier with integrated heat recovery

ABSTRACT

A drier apparatus for removing water or other liquids from various materials includes a mixer, drying chamber, separator and regenerator and a method for use of the apparatus. The material to be dried is mixed with a heated media to form a mixture which then passes through the chamber. While passing through the chamber, a comparatively cool fluid is passed counter current through the mixture so that the mixture becomes cooler and drier and the fluid becomes hotter and more saturated with moisture. The mixture is then separated into drier material and media. The media is transferred to the regenerator and heated therein by the hot fluid from the chamber and supplemental heat is supplied to bring the media to a preselected temperature for mixing with the incoming material to be dried. In a closed loop embodiment of the apparatus, the fluid is also recycled from the regenerator to the chamber and a chiller is utilized to reduce the temperature of the fluid to a preselected temperature and dew point temperature.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/881,779, filed Jul. 27, 2007 that claimed the benefit of U.S.Provisional application No. 60/834,125 filed Jul. 28, 2006 and U.S.Provisional application No. 60/899,964 filed Feb. 7, 2007 which areincorporated herein by reference.

STATEMENT REGARDING UNITED STATES GOVERNMENT SPONSORED RESEARCH ORDEVELOPMENT

The present invention was at least in part made with support from theUnited States Government under Contract No. DE-FC36-01G011037 awarded bythe Department of Energy. The United States Government has certainrights in the invention.

BACKGROUND OF THE INVENTION

The present invention is directed to improvements in driers and methodsof drying used to dry various materials, including newly harvestedgrain, wood pellets, etc. and, in particular, to driers that recover andutilize a comparatively high percentage of the energy used in the dryingprocess.

The drying industry is very large and utilizes significant amounts ofboth fossil fuels and electricity to dry various materials. While thegrain industry is not the only industry that requires significantdrying, it is indicative of the problems that exist. Just the U.S. corncrop amounts to almost nine billion bushels annually. Moisture must beremoved in order to allow the grain to be stored without significantloss due to mold, mildew and rot caused by excess retained moisture.

In theory, each pound of water removed from the grain has a latent heatof vaporization of about 1160 British thermal units (Btu's) per pound.In a highly effective dryer system, the dryer could import exactly thistheoretical amount of energy per pound of water to be removed from thegrain. In reality, the grain also takes on sensible heat and raises intemperature during the process, the flow of heating gas is not uniform,the grain is often heated more on one side of the dryer than the other,etc., such that the efficiency of all types of conventional driers iscomparatively low. Cross flow grain driers normally requireapproximately 2800 Btu per pound of water removed versus the theoreticalamount of 1160 Btu per pound.

Because the corn industry in the U.S. consumes approximately 900 milliongallons of propane and over 3200 million kilowatt-hours of electricityper year just to dry the corn and because this produces nearly twomillion tons of carbon dioxide exhaust gases per year, it is seen thatany improvement in drying efficiency can amount to significant savingsin fuel, energy and emissions. Corn is only one type of grain that mustbe dried. Further, there are many other solids, semi-solids andinitially liquid compositions that are dried each year by vaporizing aliquid component or completely evaporating most or all of an incomingstream, at considerable costs in terms of fuel, energy and undesiredemissions due to combustion of the fuels.

It is further noted that for some materials the manner of drying isimportant to prevent excessive shock to the product being dried and/orto reduce inconsistency in the dried material. For example, grainkernels can be cracked by cooling or heating too quickly, which can leadto degradation of the grain. While conventional driers may provide achosen average moisture content, the content may not be consistent.Consequently, problems are encountered in many types of conventionalcross flow grain driers where, the grain is heated and dried by airpassing perpendicularly to the flow of the grain. In such driers, thegrain on one side of the dryer that first encounters the heated air isoverly dried and may be dried too quickly or cooled too quickly so as tocause cracking and the grain on the opposite or on air discharge sidetends to be too wet. Therefore, it is also desirable to provide a dryerthat provides consistent, uniform and non stressful heating to drive offmoisture and thereafter uniform and non stressful cooling.

In some circumstances, it is also desirable to provide a closed recyclesystem for gas used in the drying process to reduce dust or otherundesirable emissions.

SUMMARY OF THE INVENTION

A dryer wherein an incoming material, especially a granular, pelletizedor other material, having removable moisture or other removable fluidtherein that is to be removed by drying is generally uniformly mixedwith a heated medium, in particular, a particulate medium, to form amixture that is hotter than the incoming material to be dried and,thereafter, allowed to flow through a drying chamber from an entrance toan exit thereof. A cooling fluid, preferably air that is ambient orrecycled, if exhaust emissions are of a concern, is counterflowedthrough the mixture from near the mixture exit to near the mixtureentrance, such that the cooling fluid is heated by the mixture duringpassage through the chamber. As used herein the term cooling fluidrefers to a drying fluid that absorbs and removes liquid, preferablymostly vapor produced by liquid to gaseous phase change, from a materialto be dried. Sensible heat transfers from the heated media to thematerial to be dried and vaporizes the moisture or other liquid to beremoved from the material, preferably by phase change. The fluid duringpassage through the chamber absorbs the moisture or vapor released fromthe material to be dried, so as to become fully saturated or, at leastpartly saturated as the fluid exists the chamber. In this manner, thefluid dries the material principally by phase change of the liquid thatwas originally contained in or on the incoming material to be dried.There is also normally cooling the material across a temperaturegradient of cool to hot from near the material exit to near the materialentrance.

At the chamber exit, the media (now comparatively cool) is separatedfrom the material to be dried, by a separator, such as an air flowseparator, a magnetic separator or especially a physical size separatorsuch as a sizing screen that allows passage of one, but not the other.For this invention, the media can be larger or smaller than the materialto be dried, when a screen is used. Other separation techniques areforeseen possible, especially where the components of the mixture are ofthe same size.

The material which at the discharge of the separator is comparativelydrier than before entering the drier is then transferred to storage orthe like. The media, which at the discharge preferably has been cooledby passage through the chamber, is then transferred back to the entranceto be mixed with the incoming material to be dried. Along the transfer,the fluid which is heated and at least partially saturated with moisturesubsequent to exiting the chamber is counter flowed past the media in aregenerator, so that the media is at least partially reheated. Thisallows the recovery of both sensible and latent heat from the fluid bythe media.

Because the media is relatively cool and the fluid is hot and at leastpartly saturated with moisture or other condensible liquid, as the fluidcools during the media heating process, moisture or other liquidcondensate forms on the media that is collected and withdrawn. In someinstances, a blow off system is applied to the heated media whereinrecycled process air or another gas is blown past the media afterheating by the fluid to remove condensate adhering to the media. Priorto mixing with the incoming material to be dried, the partially heatedmedia is passed through a makeup or supplemental heater that furtherheats the media to a preselected temperature that is determined to bebest for mixing with the incoming material to be dried.

In certain embodiments, the various fluid streams are collected,especially the gas that exits the regenerator, is collected and returnedto the drying chamber for recycle or repassing through the mixturetherein. Because the fluid that is recycled in this manner may in somecases be somewhat hotter than the fluid at the beginning of the processinitially (for example, ambient air), an intermediate chiller may beutilized to cool the fluid to a preselected temperature before flowinginto the mixture in the chamber. In this manner, the fluid is notexhausted to the atmosphere, so as to reduce dust or other undesirableemissions.

The media may be any suitable material that can function to becomeheated and convey such heat to the material to be dried. Such mediacould include rocks, ceramic or glass balls or other shapes, piecesformed of metal or the like. Preferably, the media is stable and notsignificantly damaged by recycle usage. When used with foodstuffs, suchas grain, the media must be food safe.

Therefore, the basic process in general is to mix a material to be driedwith a media that is preheated with recovered or reclaimed sensible andlatent heat to form a mixture and allow that mixture to pass in a firstdirection through a chamber. A comparatively cool fluid, especially agas such as air, is counter flowed in the opposite direction through themixture in the chamber so that the material is first heated by the mediaand then cooled or the energy state is changed by latent heat releaseassociated with the phase change of the liquid to be removed while beingdried by the fluid. The comparatively cool dry media and dry materialare separated. The heated and moisture carrying fluid is then counterflowed past the separated media and condensate is removed, so that themedia is at least partly reheated. The partially heated media is thenfurther heated by a makeup heater and returned to the incoming materialto be dried to form the mixture therewith. The process, therefore, firstheats the material to be dried and then dries the material by flowingcooling and drying fluid (generally referred to as cooling fluid herein)therethrough. The incoming comparatively cool and dry fluid becomesheated and removes moisture vaporized or evaporated from the material tobe dried as the fluid passes through the chamber. Much of the sensibleand latent heat utilized to drive moisture from the material isrecovered and reused by this overall process and especially by thereheating of the media by the fluid exiting the chamber, therebyrequiring comparatively little supplemental heat input into the mediaafter being heated by the hot fluid.

While principally counter current flow processes are described above andpreferred, both with respect to the drying of the material and thereheating of the media, it is foreseen that some processes may be atleast partially counter flow, cross-flow, concurrent flow or mixturesthereof. Further the processes may have individual sections that arecross flow, counter flow, concurrent flow or mixtures of such flow, butwhich are overall counter current flow. The process could also beconducted in sequential steps wherein a certain amount of moisture isremoved in each step, including wherein there are multiple dryingchambers that each reduce moisture a given amount in sequence whereinthe cooling fluid from all the chambers uses a single regenerator.

Objects and Advantages of the Invention

Therefore, the objects of the invention are: to provide a dryer that isespecially effective in drying material with comparatively smalleroutside energy input; to provide such a dryer that is effective inuniformly and consistently drying materials; to provide such a dryerthat initially forms a heated mixture of the material to be dried bymixing with a heated media which is then passed through a drying chamberin counter flow relation to a fluid, such as air, that is initiallycomparatively cool and that is heated and at least partially saturatedwith moisture as the fluid passes through the mixture; to provide such adryer wherein the media, when comparatively cool, is separated from thenow comparatively dry and cool material and counter flow heated by thehot fluid exiting at the material entry to the chamber and, thereafter,the media is heated by a supplemental heater to a preselectedtemperature; to provide such a dryer that can be converted to allowenclosed recycle of the fluid to reduce undesirable emissions; toprovide such a dryer that has a comparatively high efficiency whereincomparatively little heat is required from an external source such asfuel, in comparison to conventional driers; and to provide such a drierthat is easy to use, economical to build and operate and especially welladapted for the intended purpose thereof.

Other objects and advantages of this invention will become apparent fromthe following description taken in conjunction with the accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of this invention.

The drawings constitute a part of this specification and includeexemplary embodiments of the present invention and illustrate variousobjects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially schematic view of a drier in accordance with thepresent invention having a vertical drying chamber.

FIG. 1A is a drier similar to that of FIG. 1 having a fluid recyclesystem and a fluid chiller.

FIG. 2 is a partially schematic view of a first modified drier inaccordance with the present invention having a fluidized bed dryingchamber.

FIG. 2A is a drier similar to the drier of FIG. 2 having a fluid recyclesystem and a fluid chiller.

FIG. 3 is a partially schematic view of a second modified drier inaccordance with the present invention having a rotary drum dryingchamber.

FIG. 3A is a drier similar to the drier of FIG. 3 having a fluid recyclesystem and a fluid chiller.

FIG. 4 is a partially schematic view of a third modified drier inaccordance with the present invention having a vertical drying chamberand a cross flow media supplemental heater.

FIG. 4A is a drier similar to the drier of FIG. 4 having a fluid recyclesystem and a fluid chiller.

FIG. 5 is a partially schematic view of a fourth modified drier inaccordance with the present invention including a fluidized bed dryingchamber and a cross flow media supplemental heater.

FIG. 5A is a drier similar to the drier of FIG. 5 including fluidrecycle and a fluid chiller.

FIG. 6 is a partially schematic view of a fifth modified drier inaccordance with the invention showing a rotary drum drying chamber and across flow media supplemental heater.

FIG. 6A is a drier similar to the drier of FIG. 6 including fluidrecycle and a fluid chiller.

FIG. 7 is a schematic diagram of a further alternative drying chamberwherein a mixture to be dried enters one end of the chamber and acooling fluid flows generally overall counterflow to the mixture, but instages flows concurrently with the mixture.

FIG. 8 is a schematic diagram of a still further alternative dryingchamber wherein a mixture to be dried enters one end of the chamber anda cooling fluid flows generally overall counterflow to the mixture, butin stages flows cross flow relative to the mixture.

FIG. 9 is a schematic diagram of a yet further alternative dryingchamber wherein a mixture to be dried enters one end of the chamber andcooling fluid flows generally overall counterflow to the mixture, but instages the cooling fluid flows in mixed flow patterns relative to themixture.

FIG. 10 is a schematic of a further alternative regenerator whereinmedia to be heated enters from one end and comparatively hot fluid flowsoverall generally counterflow to the media, but in stages the fluidflows concurrently with the media.

FIG. 11 is a schematic of a still further alternative regeneratorwherein media to be heated enters from one end and comparatively hotfluid flows generally overall counter currently to the media, but instages the fluid flows in cross flow through the media.

FIG. 12 is a schematic of a yet further alternative regenerator whereinmedia to be heated enters from one end and comparatively hot fluid flowsgenerally overall counter current to the media, but in stages fluidflows in mixed flow patterns relative to the media.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure.

As shown in FIG. 1, the reference numeral 1 generally represents a drierin accordance with the present invention.

The drier comprises an inlet mixer 5 (that also functions to provide aheating zone or sweatbox), a drying chamber 6, a separator 7 and aregenerator system 8.

A material 12 to be dried (here corn) is fed at the arrow numbered 13into the mixer 5 from a source outside the drier 1. At the same time amedia 14 (here smooth rock of approximately one half inch diameter andlarger) that has been heated is also fed into the mixer 5 and the media14 and material 12 are subsequently mixed by flow into the mixer 5and/or by use of an alternative agitator to form a generally uniformmixture 16 of material 12 and media 14. In the present embodiment, themixture 16 has enough residence time in the mixer 5 to preferablyapproach thermal equilibrium at a common temperature. The heat transferprocess in the mixer 5 will also preferably cause the material 12 tostart to give off moisture or sweat in response to being heated by themedia 14.

The mixture 16 discharges through a lower opening 17 into a top 18 ofthe chamber 6. Airlocks 19 and 20 are provided whereat the material 12and media 14 enter the mixer 5. The chamber 6 can be round, square,rectangle, or other shapes and herein is approximately square in crosssection and is preferably insulated to reduce heat loss. It is foreseenthat in some embodiments the chamber 6 may be wider than thick or may bea modified conventional round grain bin. The chamber 6 includes a fluidcollection manifold 21 that is perforated to allow the fluid to flowinto the manifold 21 after passage through the chamber 6.

The chamber 6 of the illustrated embodiment is vertically higher ortaller than wide and is joined at the bottom to a separator 7 thatincludes a screen 23 that effectively separates the cool and dry media14 at the bottom of the chamber 6 from the material 12. The separatedmaterial 12 exits the drier 1 relatively cool and comparatively drierthan when the material 12 entered the chamber 6. When drying mostmaterials that absorb liquids, it is preferably that the fluid be agaseous fluid, typically air, but other types of fluids are alsoeffective, especially nitrogen where there is a high explosive risk, inthe presence of oxygen, provided that such fluids permit the absorptionand condensation of water vapor or other substance to be dried from thematerial 12. A fluid dispenser manifold 25 extends across the lower end26 of the chamber 6 in such a manner as to allow flow of fluid(indicated by arrows 29) through perforated walls into the chamber 6 andthrough the collected mixture 16 therein. The mixture 16 flows betweenelements of the manifolds 21 and 25 which includes perforations forreceiving and discharging fluid 29 (here air).

The regenerator system 8 includes a conveyor 32 that operably joins withthe separator 7 so as to receive media 14 therefrom and transport therelatively cool dry media to a regenerator 34. The conveyer 32 isrotated by a motor not shown. While the conveyor of the presentembodiment is located between the regenerator and the separator, it isforeseen that the conveyor could be located between the regenerator andmixer, that it could be centrally located or that it could be dividedinto sections on either side of the regenerator. The regenerator couldalso perform the function of the conveyor in some embodiments.

The regenerator 34 has a tube 35 aligned at an angle with the horizontaland an interior belt conveyor 37, driven by a motor not shown, that hasa series of media receiving pans or buckets 38 that receive the media 14from the conveyor 32 and that are mounted on a continuously rotatingbelt 40. It is foreseen that a cable or the like could also be used tomove the buckets. It is also foreseen that the regenerator could have awide range of inclination or none relative to the horizontal in someembodiments, provided that condensate can be collected and drainedtherefrom. The buckets 38 are constructed of a screen mesh that is sizedto hold the media 14, but allows passage of fluid 29 therethrough. Mostof the buckets 38 that are shown raising in the regenerator 34 are fullof media 14 and the ones going down on the opposite side are empty.

The manifold 21 is flow connected by a conduit 44, having a driving fan45 therein, with an intermediate location along the regenerator 34. Itis foreseen that fan can be also located at the entry to the chamber soas to act as a pusher. The conduit 44 opens at outlet 46 into the tube35 so that fluid (here indicated by arrow 47) flows into the tube 35counter flow to the movement of the pans 38 and eventually out a fluiddischarge 48. Suitable airlocks are provided in the regenerator 34 todirect flow of fluid therethrough.

In a final drying and heating region 51, a small side arm 50 of theconduit 44 directs a small slip stream of the fluid indicated by thearrow 54 out a secondary fluid discharge 55 into the atmosphere. Theslip stream 54 is used for the drying or blow away removal of surfacemoisture and heating of the media 14 and is a small percentage of theoverall fluid flow, preferably less than 5% by volume. Such a slipstream 54 works best when the fluid is not fully saturated.

Located between the conduit outlet 46 and the slip stream 54 is a waterblow off system 56 that includes a fan 58 to recycle gaseous fluid at ahigher velocity past the media 14 to blow beaded moisture or otherliquid from the media 14.

Subsequent to the drying and heating region 51, the media 14 enters asupplemental heating region 63. A sensor 64 measures the temperature ofthe media at the exit thereof and compares the exit temperature to apreselected desirable temperature. A heater 65 is located in the heatingregion 63 along with a fan 66 that blows fluid past the heater 65 andthrough the media 14 in the region 63 in response to the actualtemperature at the sensor 64 being below the preselected temperature.The preselected temperature is selected for the particular materialbeing dried. For example, the preselected temperature is preferably in arange from 180° to 240° F. for many materials to be dried. For some, thepreferred temperature may be higher or lower. For corn, it is preferredthat the temperature of the mixture exiting the mixer 5 be in the rangefrom 160° F. to 190° F. Upon startup additional heating by the heater 65is normally required to bring the media 14 up to temperature, since themedia 14 on a cold startup will not be preheated by the fluid exitingthe chamber 6. It is foreseen that the heater 65 may utilize manydifferent types of energy, including natural gas, propane electricalresistance, microwave, oil, biofuel and the like.

The media 14 is dumped from the buckets 38 as such leave the heatingregion 63 into a chute 69 that collects heated media (indicated by thearrow 70) at the bottom thereof and delivers the heated media 70 to themixer 5. The regenerator 8 is provided with suitable access locations,not shown, to allow the initial supply of media 14 or makeup media 14thereto and for maintenance.

In use, the wet material 12 enters the mixer 5 through an airlock 19 andis mixed with comparatively hot media 14 to form mixture 16. The mixture16 flows into and downwardly through the chamber 6 while the initiallycool fluid 29, preferably air at ambient air temperature or about 70°F., flows upwardly in counter flow through the mixture 16. The mixture16 becomes cooler and drier as it drops lower in the chamber 6 and thefluid 29 becomes hotter and more saturated with moisture as it raises inthe chamber 6. The media 14 is separated from the material 12 in theseparator 7 and transported to the bottom of the regenerator 34. Thematerial 12, preferably now about the same temperature as prior toentering the drier 1, but comparatively drier, is delivered to storageor transferred to a different location or in some embodiments directedto another pass through the drier 1, if necessary.

The comparatively cool dry media 14 is loaded onto the buckets 38 of theconveyor 37 and passes in counter flow to the comparatively hot and atleast partially saturated main stream of fluid that has exited thechamber 6. The media 14 thereby becomes hotter and moisture or otherliquid condenses on the media 14 and migrates to the bottom surface ofthe tube 35. The moisture flows down the bottom surface of the tube 35,here due to the inclination of the tube 35, and exits the drain 60.After the media 14 passes the fluid conduit outlet 46, it is blown dryby the blow dry region 56, thereafter enters the drying and heatingregion 51 with a concurrent flow of a small slip stream of fluid andthereafter is supplementally heated in the heating region 63 to thepreselected temperature, here 210° F.

Thereafter, the heated and relatively dry media 14 is mixed with theincoming material 12 in the mixer 5 and the cycle continues until allmaterial 12 is dried to a selected moisture content that is chosen forthe particular material 12 to be dried.

Shown in FIG. 1A is drier 80 that in many ways is quite similar to drier1. Consequently, only major elements and the elements that are differentare discussed in detail. Reference is made to the description of drier 1for the remainder of the description of drier 80.

Drier 80 includes a mixer 81, a drying chamber 82, a separator 83 and aregenerator 84.

The principal difference in the drier 80 as compared to the drier 1 isthat conduits 87 and 90 are provided to collect fluid exiting theregenerator 84 at outlets 91 and 92 respectfully. The conduits 87 and 90join in a common manifold 95 that recycles the fluid indicated by flowarrows 97 back to a lower chamber manifold 99 for distribution through aperforated fluid dispenser 100 into a mixture 101 in the chamber 82.Located along the manifold 95 is a chiller 105 of conventionalrefrigeration unit construction, including commercial air conditionunits, refrigeration units, heat exchanger with ambient air, heat pumpsand similar devices, having a condensate drain 106 utilizing a heatexchanger and air cooling unit (not shown) to cool the fluid in themanifold 95 to a preselected temperature, for example 70° F. The purposeof the chiller 105 is to return the fluid 97 to essentially the samestarting temperature and to adjust the dew point temperature of thefluid 97 at the bottom of the chamber 82 for each cycle thereof, so thatthe fluid 97 does not increase somewhat in temperature with each cycle.It is foreseen that the chiller could be located other places in thesystem and perform an equivalent function, such as along a conveyor 104that conveys media 115 between the separator 83 and regenerator 84, soas to remove a small amount of heat by condensing liquid at suchlocation. It is foreseen that the heat from the chiller 105 could beconserved and used to help preheat the media 115. It is also foreseenthat the chiller could be a heat pump or other suitable device forremoving heat and that such heat could be returned to the drier 80 foruse in heating the media 115 or the mixture 101 or the like.

Shown in FIG. 2 is a drier 120. The drier 120 is similar to the previousdescribed drier 1 and portions that are the same are not described againin detail, but rather reference is made to the description of drier 1.

Drier 120 has a mixer 123, a drying chamber 124, a separator 125 and aregenerator 126. The principal difference here as compared to drier 1 isthat the vertical column drying chamber of drier 1 has been replacedwith a horizontal fluidized bed chamber 130. The chamber 130 has aperforated floor 132 suspended therein which receives a mixture 133 ofmaterial 134 to be dried and heated media 135 from the mixer 123. Thechamber 130 has an enclosed outer wall 137 from which suspend a seriesof spaced upper and lower fluid flow directing baffles 139 a and 139 b.A series of upper ports 140 is connected to a series of lower ports 141by conduits 142 having a driving fan 143 therein that circulates fluidin the portion of chamber 124 that is located between each associated oradjacent pair of baffles 139 a and 139 b, such as represented by thearrows 145 from ports 140 to ports 141 and through the floor 132 tofluidize a mixture bed 144 thereon. In this manner, fluid represented byarrow 147 passes through the fluidized bed 144 and is moving counterflow to the mixture 133, while at the same time a significant flow offluid 145 is being flowed upwardly through the bed 144. The mixture bed144 is fluidized and flows generally to the right as seen in FIG. 2.Where needed, the floor 132 may be slanted toward the outlet, an opengrid chain can be drawn through the bed 144 toward the outlet or otherstructure can be used to facilitate movement of the bed 144 over thefloor 132.

Shown in FIG. 2A is a drier 160 similar to drier 120 except as describedbelow. The drier 160 has a mixer 161, a fluidized bed drying chamber162, a separator 163 and a regenerator 164. In drier 160, collectionconduits 165 and 166 collect fluid exiting the regenerator 164 atdischarge locations 167 and 168 respectively. The conduits 165 and 166join in a common manifold 170 that is in flow communication with thelocation 171 whereat the fluid enters the chamber 162 to operablyrecycle fluid as represented by arrow 172 within a substantially closedsystem. Located along the manifold 170 is a chiller 174 with a liquiddrain 175 for chilling the fluid to a preselected temperature and dewpoint temperature.

FIG. 3 shows a drier 180 which is similar to drier 1 and includes amixer 181, a drying chamber 182, a separator 183 and a regenerator 184.The drying chamber 182 differs from that of drier 1 in that it has arotary drum 185. The drum 185 includes a cylindrical shell 186 thatoperably rotates and that has a series of spaced suspended stationarybaffles 187 that urge the fluid represented by arrows 188 to passthrough a rotating mixture 189. The baffles 187 are supported by a shaft190 that extends through the shell 186. The shaft 190 and baffles 187 donot rotate with the shell 186, so that the flow of fluid 188 is alwaysbeneath a bottom 191 of the baffles 187. In the view of FIG. 3, themixture 189 moves from left to right as the fluid 188 moves from rightto left through the drum 185.

FIG. 3A shows a drier 200 that is similar to drier 180 and has a mixer201, drying chamber 202, a separator 203 and a regenerator 204. Thedrier 200 differs from drier 180 in that it includes a fluid collectionand return manifold system 206 with collection conduits 207 and 208 thatcollects fluid exiting the regenerator 204 and returns the fluidrepresented by the arrow 205 to the drying chamber 202. The returnmanifold system 206 also includes a fluid chiller 210 for chilling thefluid to a state having a preselected temperature and dew pointtemperature with a liquid drain 211.

Shown in FIG. 4 is a drier 240 that is further similar to drier 1 inthat it has a mixer 241, a drying chamber 242, a separator 243 and aregenerator 244. The regenerator 244 differs from that of drier 1 inthat there is a vertical tower 250 having an internal bucket conveyor251 that conveys media 252 from a lower end 253 to an upper end 254thereof and discharges the media 252 into a hopper and heating chamber256 that is part of the regenerator 244. The media 252 in the heatingchamber 256 is located above a series of rotating gates 257 that feedthe media 252 therethrough by gravity. Fluid indicated by arrows 260 anddriven by fan 261 upon exiting the chamber 242 is conveyed by a manifold262 to beneath the gates 257 so that the fluid which is hot passesthrough the gates 257 and lower structure of the heating chamber 256, soas to heat the media 252. Subsequently, the media 252 collects at thechute 265 and passes through a pair of rotating foam rollers 267 at nip268 which function to substantially remove the moisture condensed on themedia 252. Squeegees 270 operably squeeze water from the rollers 267.Collected moisture indicated by the arrow 269 exits at drain 271.

A secondary or supplemental cross flow heater 272 provides additionalheating to the partially heated media 252 to bring it to a desired orpreselected temperature. Bypass plenums 274 have control dampers 275therein and allow bypass flow of fluid on startup to initiate the dryingprocess. Alternatively, it is foreseen that the fan 261 could be stoppedduring startup.

Drier 280 is shown in FIG. 4A and includes a mixer 281, drying chamber282, separator 283 and regenerator 285. The drier 280 is like drier 240except the fluid exiting the regenerator 285 and indicated by arrows 287is collected in a manifold 288 and returned to the bottom of the dryingchamber 282 in a generally closed loop through a chiller 290 having adrain 291. The chiller 290 being for chilling the fluid to a preselectedtemperature and dew point temperature.

FIG. 5 shows a drier 300 that is similar to previous fluidized bed drier120 in part and prior drier 240 in part. In particular, drier 300includes a mixer 301, drying chamber 302 that provides a fluidized bed303 of the mixture 304 to be dried, a separator 305 and a regenerator306 which is similar to regenerator 244 except that media 308 isreturned by conveyor 309 for reheating.

Drier 320 of FIG. 5A is similar to drier 300 and includes mixer 321,drying chamber 322, separator 323 and regenerator 324. Drier 320 alsoincludes a manifold 325 collecting fluid exiting the regenerator 324 andreturning the fluid to the drying chamber 322 through a chiller 326 forchilling the fluid to a preselected temperature and dew pointtemperature and having a drain 327.

Shown in FIG. 6 is a drier 350 having a mixer 351, drying chamber 352,separator 353 and regenerator 354. The drying chamber 352 is similar topreviously described chamber 182 and the regenerator 353 is similar tothat of the previous regenerator 306. A conveyor 355 carries media 356from the separator 353 to the top of the regenerator 354 for reheating.

Shown in FIG. 6A is a drier 380 that is similar to drier 350 andincludes a mixer 381, drying chamber 382, a separator 383 and aregenerator 384. The drier 380 includes a fluid collection manifold 385with a chiller 386 having a drain 387 to operably return fluid from theregenerator 384 to the chamber 382 at a preselected temperature and dewpoint temperature.

Shown schematically in FIG. 7 is an alternative drying chamber 401 thathas a plurality of compartments 402 to 404, although it is foreseen thatany number of multiple chambers could be utilized. A mixture 406 to bedried flows generally from left to right through the chamber 401,passing through each compartment 402 to 404 in sequence. A drying andcooling fluid 408 flows overall generally counter flow to the mixture406, but in each of the compartments 404 to 402 sequentially the fluid408 flows concurrently with the mixture 406. Suitable baffles andairlocks are provided to allow the flows. It is foreseen that for someconfigurations of such a drier that a plurality of individualcompartments with fixed sides may not be required, but rather sectionsor regions may be designed to direct flow.

Shown schematically in FIG. 8 is an alternative drying chamber 421 thathas a plurality of compartments 422 to 424, although it is foreseen thatany number of multiple chambers could be utilized. A mixture 426 to bedried flows generally from left to right through the chamber 421,passing through each compartment 422 to 424 in sequence. A drying andcooling fluid 428 flows overall generally counter flow to the mixture426, but in each of the compartments 424 to 422 in sequence the fluid428 flows cross flow relative to the mixture 426. Suitable baffles andairlocks are provided to allow the flows. It is foreseen that for someconfigurations of such a drier that a plurality of individualcompartments with fixed sides may not be required, but rather sectionsor regions may be designed to direct flow.

Shown schematically in FIG. 9 is an alternative drying chamber 441 thathas a plurality of compartments 442 to 444, although it is foreseen thatany number of multiple chambers could be utilized. A mixture 446 to bedried flows generally from left to right through the chamber 441,passing through each compartment 442 to 444 in sequence. A drying andcooling fluid 448 flows overall generally counter flow to the mixture446, but in each of the compartments 444 to 442 the fluid 448 flowsdifferently with respect to each other. In compartment 444 the fluid 448flows counter currently with the mixture 446, in compartment 443 thefluid 448 flows cross flow with respect to the mixture 446 and incompartment 442 the fluid 448 flows concurrently with the mixture 446.Such combination of different flow paths is generally referred to hereinas mixed flow and it is foreseen that such could be any combination ofsuch flow paths in different compartments. In some instances differentor mixed flow paths are combined in the same compartment, such as isshown in FIG. 2 wherein each compartment has both concurrent flow andcross flow of the fluid passing therethrough. It is foreseen thatunitary flow paths within individual chambers or other combinations ofcombined or sequential mixed flows in various chambers may be utilizedin certain embodiments. It is foreseen that mixed flows of variouscombinations may be utilized in different regions or compartmentswherein only a single flow path of fluid occurs relative to the media ineach separate compartment or certain flow paths can be combined within asingle compartment such as counter current and cross flow. Suitablebaffles and airlocks are provided to allow the flows. It is foreseenthat for some configurations of such a drier that a plurality ofindividual compartments with fixed sides may not be required, but rathersections or regions may be designed to direct flow.

Shown schematically in FIG. 10 is an alternative regenerator 451. Theregenerator 451 has a plurality of compartments 452 to 454, although itis foreseen that any plural number of compartments may be utilized.Media 456 in a comparatively cool state enters the regenerator 451passing from left to right and flows sequentially through eachcompartment 452 to 454. A hot fluid 458 flows overall generally countercurrent to the media 456, but within each of the compartments 454 to 452in sequence the fluid flows concurrently with the media 456. Suitablebaffles and airlocks are provided to allow the flow. It is foreseen thatfor some configurations of such a drier that a plurality of individualcompartments with fixed sides may not be required, but rather sectionsor regions may be designed to direct flow.

Shown schematically in FIG. 11 is an alternative regenerator 461. Theregenerator 461 has a plurality of compartments 462 to 464, although itis foreseen that any plural number of compartments may be utilized.Media 466 in a comparatively cool state enters the regenerator 461passing from left to right. A hot fluid 468 flows overall generallycounter current to the media 466, but within each of the compartments464 to 462 in sequence the fluid 468 flows cross flow through the media466. Suitable baffles and airlocks are provided to allow the flow. It isforeseen that for some configurations of such a drier that a pluralityof individual compartments with fixed sides may not be required, butrather sections or regions may be designed to direct flow.

Shown schematically in FIG. 12 is an alternative regenerator 481. Theregenerator 481 has a plurality of compartments 482 to 484, although itis foreseen that any plural number of compartments may be utilized.Media 486 in a comparatively cool state enters the regenerator 481passing from left to right. A hot fluid 488 flows overall generallycounter current to the media 486, but within each compartments 484 to482 in sequence the fluid 488 flows in mixed flow relative to the media486. In particular in chamber 484 the fluid 488 flows counter current tothe media 486, in chamber 483 the fluid 488 flows cross flow through themedia 486 and in chamber 482 the fluid 488 flows concurrently with themedia 486. It is foreseen that mixed flows of various combinations maybe utilized in different compartments wherein only a single flow path offluid occurs relative to the media in each separate compartment orcertain flow paths can be combined within a single compartment or regionsuch as counter current and cross flow. Suitable baffles and airlocksare provided to allow the flow. It is foreseen that for someconfigurations of such a drier that a plurality of individualcompartments with fixed sides may not be required, but rather sectionsor regions may be designed to direct flow.

It is foreseen that the fluid driving mechanism, such as fan 45 of dryer1 of the first embodiment could be located downstream of the dryingchamber (that is, in the fluid path after the fluid exits the chamber)and pull the fluid through the chamber, such as chamber 6 in drier 1 orcould be upstream of the chamber (that is, prior to the fluid enteringthe chamber) and push the fluid through.

It is foreseen that supplemental heat could be added to the drier tomake up for losses in the method at many locations. In the embodimentsshown, the heat is added subsequent to the heat exchange between thefluid and the media in the regenerator. However, the supplemental heatcould be added to the material to be dried, to the media while in theregenerator or to the fluid prior to entering the regenerator and inother ways.

While a continuous counter flow process is described for the chamber andmost of the regenerator in the embodiments described, it is foreseenthat batch processes could be utilized using one or a series ofsequential batch operations. Further, it is foreseen that the flow offluid into the mixture in the chamber and into the media in theregenerator could be step wise cross flow, step non counter current flowand other flow configurations including mixed configurations whereineach segment or section may encounter one or more different types offlow, but the overall general path of flow of the fluid is countercurrent to the material to be dried in the chamber.

It is foreseen that the mixture may be conveyed through the chamberand/or the regenerator by other types of systems including, but notlimited to, round plate systems, tunnel driers, column driers with flowdirecting auger especially upward flow column driers, driers using beltsto convey mixture therethrough, vibratory inclined plane elevatordriers, vibratory spiral elevator driers, modified conventional roundbin grain driers, disc driers, screw driers and plough driers, as wellas driers of other types especially suitable to the material to be driedand various mixtures of drier type.

It is further foreseen that in the rotary drum embodiments of the drier,that the baffles could be eliminated by making the drum of a relativelynarrow cross section so that the fluid flows through the mixture in thechamber.

It is also foreseen that although the embodiments shown are principallydirected to removing moisture from a material to be dried, that theprocess can be used to remove other evaporatable liquids such assolvents or the total vaporization of an incoming fluid as anevaporator. The process of the invention is highly adaptable to anysituation where there is a vaporizable and condensible component thatcan be carried by a carrier or drying (here cooling) fluid so as to beremoved from another component or fully evaporated and thatthermodynamically saves energy over conventional processes. It is notedthat in some chemical processes the component to be removed may not bewasted, but rather recovered for reuse. The latter is especially true insolvent recovery.

It is foreseen that in certain embodiments that the drying chambers ofthe process may be operated under a partial or full vacuum in order toenhance evaporation of a fluid to be dried from the material to bedried, especially to reduce energy consumption or to increase capacity.

It is foreseen that multiple drying chambers may be utilized with asingle regenerator so that fluid from separate chambers all enters thecommon regenerator and all media also enters the regenerator forreheating. For example, separate compartments or chambers could bespaced and the cooling fluid could pass between the different chambers,or may return to the regenerator after exiting each chamber such as isshown in FIG. 1. With separated chambers, different materials to bedried by use of different feed paths or materials at different moisturecontent could be dried in separate chambers.

While the illustrated embodiments physically mix the material to bedried with the media, it is foreseen that in some instances the hotmedia could flow along side the material to be dried, but be separatedby perforated walls in which case cooling fluid in a mixture of crossand counter current flow could pass through both whereby the fluid wouldbe heated as well as the material by the media and the fluid wouldwithdraw moisture or other liquids from the material. It is alsoforeseen that a heated liquid may be flowed in closed tubes passingthrough the material to be dried and wherein the liquid flows generallyconcurrent with the material to be dried and a cross flow and countercurrent flow fluid flows through the material to be dried such that thefluid and the material are heated by the liquid in the tubes which mayinclude heat transfer fins and the like, so that the fluid removesmoisture or other liquids from the material to be dried.

While air and nitrogen are the most likely fluids to be used in aprocess of this type, it is foreseen that other fluids such as argon orthe like may be used. Furthermore, while particular materials to bedried have been mentioned herein, it is foreseen that a wide variety ofmaterials may be dried, including particulates and other granularmaterials, powders, flakes, pastes, slurries, and solids in general.Such materials are not restricted to but may be represented byfoodstuffs, such as grains, beans, dog food, mixes, meals and flours;chemicals such as clays, coals, sand; and processed materials, such aspaper and the like. Still furthermore, it is foreseen that the media maybe chosen from a wide range of materials including, but not limited to,crystals, minerals, salts, sands, metal pellets and balls, pea gravel,ceramic pellets or balls, composite materials such as ceramic orconcrete pellets with imbedded iron filings and the like.

It is foreseen that, when a heat pump is utilized to chill inlet air,either recycled or ambient in open looped systems, the energy removedmay at least partially be utilized to heat material to be dried and/ormedia and thereby reduce energy consumption or increase capacity.

It is to be understood that while certain forms of the present inventionhave been illustrated and described herein, it is not to be limited tothe specific forms or arrangement of parts described and shown.

1. A method of drying a wet material comprising the steps of: a) heatingthe material to be dried to a heated state; b) passing the material tobe dried in a heated state into a drying chamber; c) flowing air that isinitially cool compared to the material into the drying chamber; and d)passing the air, while in the drying chamber, in generally overallcounterflow to the material and so as to absorb moisture and heat fromthe material in the drying chamber.
 2. The method according to claim 1wherein the material is fully heated to the heated state thereof priorto entering the drying chamber and the air flows counter flow to thematerial in the heating chamber.